The Major Events in the Chinese Calendar Reform History

The History of Chinese Lunar Calendar

Chinese calendar combines solar yearly cycle, lunar monthly cycle and Stem-Branch daily cycle. The cycles of the Sun and the Moon never have a matching point. Ancient Chinese must adjust the calendar every one hundred year. It's very often that every Chinese emperor published a new calendar for new nation.

Many historical books were burned during the first emperor of China in Chin Dynasty (221 B.C.). There is no solid evidence of the first Chinese Lunar Calendar. But Chinese calendar has a Stem-Branch counting system, which is a cycle of 60. The first king of China is Yellow King . According to the historical document, Yellow King used the day of Winter Solstice as the first day of the year in the Rat month. The first Stem-Branch is Wooden Rat. Chinese trace back the Yellow King should found the nation in 2697 B.C.

We have about 365 days a year. A new moon to another new moon takes about 29.5 days. 12 lunar months takes 29.5 X 12 = 254 days. The cycle of Moon is off the cycle of Sun 11 days a year. After three years, the cycle of Moon has extra 33 days. The lunar calendar needs to add an extra lunar month to match up the cycle of the Sun. The history of the Chinese Lunar Calendar focused on how to add that lunar leap month into the calendar.

The First Day of the Chinese Calendar Year

Shiah
Dynasty (2205 B.C.) used the Tiger month as
the first month of the year Chou Dynasty (1122 B.C.) used the
Rat (Winter Solstice) month as the first month of the year
Yin Dynasty (1401 B.C.) used the Cow month
as the first month of the year
Chin Dynasty (221 B.C.) used the
Pig month as the first month of the year
Han (104 B.C.) used the Tiger month as
the first month of the year
8-22 (A.D.) used used the Cow month
as the first month of the year for a short period

Beginning Time of Chinese Lunar and Solar Months

In order to find out the good solution for the Lunar Leap
month, ancient Chinese astronomers had been looking for the common cycle of
Sun and Moon. They studied the length of lunar and solar months, the length of
a day and year, the number of lunar months in a year and so on, then made many changes in the calendar system. For example, in
Yin Dynasty (1401 B.C.), Chinese
calendar determined a Leap Month by a lunar month without a Sector
Point instead of a Center Point. The major changes in the Chinese calendar reform history
were the definition of
the beginning time of a lunar month and a solar month.

Before 619 A.D., Chinese used Mean Moon times and
Mean Sun times to determine the Leap Months over one thousand
year long.

After 619, during
Tang Dynasty, Chinese used True Moon times and
Mean Sun times to assign the Leap Months for about another one thousand
year. That means the new moon time is much easier to observe than the sun longitude position in the sky.

After 1645,
Ching Dynasty, Chinese used True Moon times and
True Sun times to find the Leap Month
locations. That's because Ching Dynasty imported modern astronomical instruments and had the ability to observe precise the Sun and Moon positions in the
sky during years.

The Mean Moon time is the length of a lunar month is the average length of lunar months a year.
The True Moon time is the length of a lunar month is the length between two new moons.
The Mean Sun time is the length of a solar month is the average length of solar months in a year.
The True Moon time is the length of a lunar month is the length between two solar Sector Points.

After Ching Dynasty, China government began to use
the Gregorian Calendar instead of lunar month for daily activities.

The First Day of Chinese Calendar Cycle

Many ancient Chinese astronomers in different dynasties kept trying to calculate back and
searching for the beginning of the Chinese Calendar cycle. The theoretic day of the starting point of Chinese
Calendar is that the day must be

Sun and Moon were on the same position in the sky at midnight, which must be
a New Moon Day